Epidemiology

Contact dermatitis is one of the most common inflammatory dermatoses seen in the dermatologist’s office and includes allergic contact dermatitis (ACD), irritant contact dermatitis (ICD), photoallergic contact dermatitis, photoirritant contact dermatitis, and protein contact dermatitis.[1]​ In one meta-analysis of 28 studies and over 20,000 individuals, the worldwide prevalence of contact dermatitis in the general population is estimated to be 20.1%.[2] ICD accounts for up to 80% of contact dermatitis and ACD accounts for nearly 20%, with the remainder making up much smaller proportions. 

​Contact dermatitis is the most common occupational skin disease, with ICD being the most common variant. Certain industries are especially susceptible to occupational ICD including hairdressing, construction, food service, health care, and metallurgy.[3]​ Out of 1019 new diagnoses of occupational skin disease reported by dermatologists in the UK in 2019,876 (86%) of these were contact dermatitis.[4] According to the British Association of Dermatologists, between 4% and 7% of dermatological consultations in secondary care are for contact dermatitis.[5]

ACD affects an equal proportion of adults and children.[6]​ ACD may affect up to 20% of children and it has been documented in patients as young as 6 months.[7][8]​​​​ Children may be more susceptible to developing ICD, particularly those with an impaired skin barrier function such as in eczema.[9]​ Adult women are affected slightly more than adult men overall but there have been no statistically significant sex differences noted in children.[2][10]​​​ Sex differences may be attributed to social and environmental factors: for example, exposure to allergens such as jewellery may be more common in women than in men.

Few studies have examined racial differences in contact dermatitis. A study from the North American Contact Dermatitis Group (NACDG) from 1998-2006 showed similar prevalence of ACD and ICD among black and white people referred for patch testing.[11]​ A more recent study using data from 2007-2016 showed that the prevalence of positive patch reaction was similar between white, black, Latino, and Asian people referred for patch testing.[12]

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